Oversized 400

[ggdav]

Since I'm endlessly chasing this noise in my motor, and the bikes been underwater, and it's got 84000 on the clock I've decided the old girl deserves a full rebuild.

There's a cheap 0.5mm (64.5) oversized piston kit available for them, but has anyone gone bigger than that? I can get a pair of pistons made reasonably cheap through work. How big can I go without swapping out the barrels so I can keep the 400cc stamped ones as my local track has a 400cc class

[6]

How big can I go without swapping out the barrels so I can keep the 400cc stamped ones as my local track has a 400cc class

Scandalous




I have absolutely no idea. We don't have those engines over here. I'm sure one of our off continent members would know.

I would imagine, you can go a good ways... But that's just a hunch.

[DrPMC]

This looks like a useful thread for you: https://www.hawkgtforum.com/forum/ho...a-big-bore-kit

If you’ve got access to precision engineering facilities it may be possible to bore out the small end of the the 400 conrods to use the VT500 pistons specified?

On a related issue, once you know the deck height of the 400 pistons and the diameter of the pistons you could search the websites of JE Pistons and/ or Wisco and see if there are any other options. I’ve used a Google advanced search using this data and limited to just the relevant site and it usually comes up with possibilities. I think I searched on the wrist (gudgeon) pin dia.